1. Field of the Invention
This invention pertains to an apparatus and process for producing a multi-layered batt by forming a plurality of thin webs of fibers, contacting each web with particles of a copolymer of vinyl chloride and vinylidene chloride, subsequently forming each web into a batt layer, each subsequent batt layer being formed on top of a first formed batt layer, and then heating the resultant composite batt.
2. Description of the Prior Art
Processes for forming layered composite batts using a plurality of garnett machines operating in parallel and perpendicular to a traveling belt are known and described, for example, in U.S. Pat. No. 2,528,091. The bonding agent preferred in that patent was described as an aqueous solution of an "A" stage phenol formaldehyde alone or admixed as by an emulsification with a lubricant such as petroleum oil. This bonding agent was to be applied by means of spray guns directed to the web as the web moves onto a "camel-back" lapper which reciprocatively distributed the web onto the moving belt. This process has a distinct disadvantage of unnecessarily increasing the weight of the composite batt produced and requires unnecessarily large and high power consuming ovens to dry cure the aqueous binder so that individual fibers of the webs are bonded together. The process had the additional disadvantage of repeatedly breaking the web due to the force of the spray which blows holes in the web as the binder material is applied.
U.S. Pat. No. 2,723,707 attempted to prevent the destruction of the thin web by attaching the means for distributing the liquid binder in such a manner as to travel with the "camel-back" mechanism and applying the binder between folds of the webs as it was formed into a batt layer. This process still required the large energy consuming drying mechanism and ovens to cure the dilute aqueous binder.
Completely dry processes for forming fibrous batts are known and are described, for example, in U.S. Pat. No. 3,765,971. However, even this dry process suffers from a number of disadvantages. It has been difficult or impossible to uniformly admix the particulate binding agent with the fibers to be bound thus causing the resultant batt to have non-uniform strength. Additionally, practical dry adhesives which are useable with a wide range of fibers have been particularly hard to identify, thus requiring that any layered batt be manufactured from a single class of fibers.